Closed-conduit ei



(No Model.)

. W. B. POTTER.

GLOSED GONDUIT ELECTRIC RAILWAY. No. 589,792. Patented Sept. 7,1897.

\M NEEEEE.

UNITED STATES PATENT union.

IVILLIAM 13. POTTER, OF'SCHEI EOTADY, NElV YORK, ASSIGNOR. TO THEGENERAL ELECTRIC COMPANY, OF NEIV YORK.

CLOSED-GONDUIT EiECTRlC RAILWAY.

SPECIFICATION forming part of Letters Patent No. 589,792, datedSeptember 7', 1897.

Application filed November 18, 1896. Renewed June 30, 1897. Serial No.648,008. (No model-J To all whom/ it 71m concern:

Be it known that I, IVILLIAM B. POTTER, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements inClosed-Conduit Electric Railways, (Case No. 460,) of which the followingis a specification.

My invention relates to surface-contact systems of supply for! electricrailways, and has for its object to provide for such systems a safetydevice by which any leakage-current will serve to open a switch whichmay by accident have remained closed, instead of increasing (as in othersystems) the danger of the switch sticking. v

To accomplish the purposes of my invention, I surround the contactstudsor sectional conductors with a metallic box or inclosing band andconnect the band or box to the wire or return circuit through adifferential coil upon the pick-up magnet of the switch. Anyleakage-current seeking ground through the box and its lead will passthrough the coil and demagnet-ize and open the switch.

It is immaterial in the practice of my invention which one of the setsof sectional conductors I prefer to employ is provided with the devicementioned. It is possible in. most cases to use the high-potentialstuds, or the negativestuds or conductors may also be employed, or, ifit be desired, both may be so protected. So, also, the coilfurnishingsafety to each contact may be upon the core of its own switch alone orthe box may be grounded through coils upon more than one of theswitches. These are all immaterial-variations not affecting the materialessence of my invention. Where several coils are thus arranged upon oneswitch, it is preferred that they should have separate grounds, so thatthe breaking of the common ground connection would not serve to cripplethe device.

The accompanying drawing shows my invention, it being a diagram of thesafety device and its connections.

A A are the track-rails; B B O C, the sectional conductors or contacts;H, the feeder.

G G are the pick-up switches, provided with operating-coils g andcontacts 9 g by which the connection from the feeder H to the positivestuds 13 Bis completed. A motorcar provided with motors M M and astorage battery E, also sliding contacts F F, travels upon the line ofway.

At I I, surrounding but insulated from the positive contacts B B, areindicated, diagrammatically, the safety, gro unds,consistin g of metalboxes connected each through coils g 9 respectively, upon the switches GG to ground. Each of these contacts is thus connected to one of theswitches and any leakage-current from the box will open the switch.

The system of connections for operating the switches shown in this caseI have not claimed, as it is covered in my application, Serial No.607,998, filed October 6, 1896.

In dotted lines I have shown the safety device applied to the negativesectional conductor O, being grounded, as in the case of the studs B,through the differential coil g upon each of the switches G. As before,any leakage-current which ordinarily would reach the stud G and bypassing through the coil 9 pick up the switch is now intercepted by theboX I, passes through the differential coil 9 and serves to hold theswitch open or to open it if it should be stuck. The power of the coilsis of course to be proportioned to the work to be done, and ordinarilythe auxiliary coils serving to demagnetize and open the switch wouldhave less power than the pickup coil, inasmuch .as the leakagecurrentwould necessarily be of comparatively small volume and moderatepotential, while the pick-up coil would carry full current.

I have used the term differential in describing my invention, meaningthereby to describe the action of the leakage-current in opening theswitch as distinguished from closing it, rather than in its technicalsense. Ordinarily I prefer that the winding should be, as illustrated,upon a separate core, acting to open the switch, and not differentiallywound upon the same core as the pick-up coil, as the latter arrangementis not so reliable.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In a surface-contact system of supplyfor electric railways, a safetydevice comprising ground and to the second set of sectional conductorsfor closing said switches, circuits for leakagecurrent arranged tointercept current tending to leak from the first to the second set ofsectional conductors, and magnets in said last-named grounded circuitsfor opening the circuit between the positive feeder and the sectionalconductors.

In. witness whereof I have hereunto set my hand this 4th day ofNovember, 1896.

V ILLIAM B. POTTER.

\V i tnesses: Y B. B. HULL, O. L. HAYNES.

